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  • 1. Arimoto, M.
    et al.
    Kanai, Y.
    Ueno, M.
    Kataoka, J.
    Kawai, N.
    Tanaka, T.
    Yamamoto, K.
    Takahashi, H.
    Mizuno, T.
    Fukazawa, Y.
    Axelsson, Magnus
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kiss, Mózsi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Marini Bettolo, Cecilia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Carlson, Per
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Chen, P.
    Craig, B.
    Kamae, T.
    Madejski, G.
    Ng, J. S. T.
    Rogers, R.
    Tajima, H.
    Thurston, T. S.
    Saito, Y.
    Takahashi, T.
    Gunji, S.
    Bjornsson, Ca.
    Larsson, S.
    Ryde, Felix
    Bogaert, G.
    Varner, G.
    Performance assessment study of the balloon-borne astronomical soft gamma-ray polarimeter PoGOLite2007In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 40, no 2, p. 438-441Article in journal (Refereed)
    Abstract [en]

    Measurements of polarization play a crucial role in the understanding of the dominant emission mechanism of astronomical sources. Polarized Gamma-ray Observer-Light version (PoGOLite) is a balloon-borne astronomical soft gamma-ray polarimeter at the 25-80 keV band. The PoGOLite detector consists of a hexagonal close-packed array of 217 Phoswich detector cells (PDCs) and side anti-coincidence shields (SASs) made of BGO crystals surrounding PDCs. Each PDC consists of a slow hollow scintillator, a fast scintillator and a BGO crystal that connects to a photomultiplier tube at the end. To examine the PoGOLite's capability and estimate the performance, we conducted experiments with the PDC using radioisotope 241Am. In addition, we compared this result with performance expected by Monte Carlo simulation with Geant4. As a result, we found that the actual PDC has the capability to detect a 100 m Crab source until 80 keV.

  • 2. Axelsson, Magnus
    et al.
    Engdegard, Olle
    KTH, School of Engineering Sciences (SCI), Physics.
    Ryde, Felix
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Larsson, S.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Hjalmarsdotter, L.
    Kiss, Mószi
    KTH, School of Engineering Sciences (SCI), Physics.
    Bettolo, C. Marini
    KTH, School of Engineering Sciences (SCI), Physics.
    Arimoto, M.
    Bjornsson, C. I.
    Carlson, Per
    KTH, School of Engineering Sciences (SCI), Physics.
    Fukazawa, Y.
    Kamae, T.
    Kanai, Y.
    Kataoka, J.
    Kawal, N.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Madejski, G.
    Mizuno, T.
    Ng, J.
    Tajima, H.
    Takahashi, T.
    Tanaka, T.
    Ueno, M.
    Varner, G.
    Yamamoto, K.
    Measuring energy dependent polarization in soft gamma-rays using compton scattering in PoGOLite2007In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 28, no 3, p. 327-337Article in journal (Refereed)
    Abstract [en]

    Linear polarization in X-and gamma-rays is an important diagnostic of many astrophysical sources, foremost giving information about their geometry, magnetic fields, and radiation mechanisms. However, very few X-ray polarization measurements have been made, and then only mono-energetic detections, whilst several objects are assumed to have energy dependent polarization signatures. In this paper, we investigate whether detection of energy dependent polarization from cosmic sources is possible using the Compton technique, in particular with the proposed PoGOLite balloon-experiment, in the 25-100 keV range. We use Geant4 simulations of a PoGOLite model and input photon spectra based on Cygnus X-1 and accreting magnetic pulsars (100 mCrab). Effective observing times of 6 and 35 h were simulated, corresponding to a standard and a long duration flight, respectively. Both smooth and sharp energy variations of the polarization are investigated and compared to constant polarization signals using chi-square statistics. We can reject constant polarization, with energy, for the Cygnus X-1 spectrum (in the hard state), if the reflected component is assumed to be completely polarized, whereas the distinction cannot be made for weaker polarization. For the accreting pulsar, constant polarization can be rejected in the case of polarization in a narrow energy band with at least 50% polarization, and similarly for a negative step distribution from 30% to 0% polarization.

  • 3.
    Jackson, Miranda
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kiss, Mózsi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Mallol, Pau
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Bettolo, Cecilia Marini
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ryde, Felix
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Rydström, Stefan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Varner, G.
    Yoshida, H.
    PoGOLite: a balloon-borne soft gamma-ray polarimeter2009In: 2009 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOLS 1-5  / [ed] Yu B, 2009, p. 449-453Conference paper (Refereed)
    Abstract [en]

    PoGOLite is a balloon-borne X-ray polarimeter, designed to measure the polarization of 25-80 keV X-rays. It is scheduled for a pathfinder flight in August 2010. This paper outlines the scientific motivation and the status of preparations of the payload.

  • 4. Kamae, Tuneyoshi
    et al.
    Andersson, Viktor
    KTH, School of Engineering Sciences (SCI), Physics.
    Arimoto, Makoto
    Axelsson, Magnus
    Bettolo, Cecilia Marini
    KTH, School of Engineering Sciences (SCI), Physics.
    Björnsson, Claes-Ingvar
    Bogaert, Gilles
    Carlson, Per
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Craig, William
    Ekeberg, Tomas
    KTH, School of Engineering Sciences (SCI), Physics.
    Engdegård, Olle
    KTH, School of Engineering Sciences (SCI), Physics.
    Fukazawa, Yasushi
    Gunji, Shuichi
    Hjalmarsdotter, Linnea
    Iwan, Bianca
    KTH, School of Engineering Sciences (SCI), Physics.
    Kanai, Yoshikazu
    Kataoka, Jun
    Kawai, Nobuyuki
    Kazejev, Jaroslav
    KTH, School of Engineering Sciences (SCI), Physics.
    Kiss, Mozsi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Larsson, Stefan
    KTH, School of Engineering Sciences (SCI), Physics.
    Madejski, Grzegorz
    Mizuno, Tsunefumi
    Ng, Johnny
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Rydé, Felix
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Suhonen, Markus
    KTH, School of Engineering Sciences (SCI), Physics.
    TaJima, Hiroyasu
    Takahashi, Hiromitsu
    Takahashi, Tadayuki
    Tanaka, Takuya
    Thurston, Timothy
    Ueno, Masaru
    Varneri, Gary
    Yamamoto, Kazuhide
    Yamashita, Yuichiro
    Ylinen, Tomi
    KTH, School of Engineering Sciences (SCI), Physics.
    Yoshida, Hiroaki
    PoGOLite - A high sensitivity balloon-borne soft gamma-ray polarimeter2008In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 30, no 2, p. 72-84Article in journal (Refereed)
    Abstract [en]

    We describe a new balloon-borne instrument (PoGOLite) capable of detecting 10% polarisation from 200 mCrab point-like sources between 25 and 80 keV in one 6-h flight. Polarisation measurements in the soft gamma-ray band are expected to provide a powerful probe into high energy emission mechanisms as well as the distribution of magnetic fields, radiation fields and interstellar matter. Synchrotron radiation, inverse Compton scattering and propagation through high magnetic fields are likely to produce high degrees of polarisation in the energy band of the instrument. We demonstrate, through tests at accelerators, with radioactive sources and through computer simulations, that PoGOLite will be able to detect degrees of polarisation as predicted by models for several classes of high energy sources. At present, only exploratory polarisation measurements have been carried out in the soft gamma-ray band. Reduction of the large background produced by cosmic-ray particles while securing a large effective area has been the greatest challenge. PoGOLite uses Compton scattering and photo-absorption in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators surrounded by a BGO anticoincidence shield and a thick polyethylene neutron shield. The narrow Held of view (FWHM = 1.25 msr, 2.0 deg x 2.0 deg) obtained with detector cells and the use of thick background shields warrant a large effective area for polarisation measurements (similar to 228 cm(2) at E = 40 keV) without sacrificing the signal-to-noise ratio. Simulation studies for an atmospheric overburden of 3-4 g/cm(2) indicate that neutrons and gamma-rays entering the PDC assembly through the shields are dominant backgrounds. Off-line event selection based on recorded phototube waveforms and Compton kinematics reduce the background to that expected for a similar to 100 mCrab source between 25 and 50 keV. A 6-h observation of the Crab pulsar will differentiate between the Polar Cap/Slot Gap, Outer Gap, and Caustic models with greater than 5 sigma significance; and also cleanly identify the Compton reflection component in the Cygnus X-1 hard state. Long-duration flights will measure the dependence of the polarisation across the cyclotron absorption line in Hercules X-1. A scaled-down instrument will be flown as a pathfinder mission from the north of Sweden in 2010. The first science flight is planned to take place shortly thereafter.

  • 5. Kanai, Y.
    et al.
    Kataoka, J.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ryde, Felix
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Rydstrom, S.
    Takahashi, T.
    Thurston, T. S.
    Varner, G.
    Kiss, Mózsi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Marini Bettolo, Cecilia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Larsson, Stefan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    A Monte Carlo method for calculating the energy response of plastic scintillators to polarized photons below 100 keV2009In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 600, no 3, p. 609-617Article in journal (Refereed)
    Abstract [en]

    The energy response of plastic scintillators (Eljen Technology EJ-204) to polarized soft gamma-ray photons below 100 keV has been studied, primarily for the balloon-borne polarimeter, PoGOLite. The response calculation includes quenching effects due to low-energy recoil electrons and the position dependence of the light collection efficiency in a 20 cm long scintillator rod. The broadening of the pulse-height spectrum, presumably caused by light transportation processes inside the scintillator, as well as the generation and multiplication of photoelectrons in the photomultiplier tube, were studied experimentally and have also been taken into account. A Monte Carlo simulation based on the Geant4 toolkit was used to model photon interactions in the scintillators. When using the polarized Compton/Rayleigh scattering processes previously corrected by the authors, scintillator spectra and angular distributions of scattered polarized photons could clearly be reproduced, in agreement with the results obtained at a synchrotron beam test conducted at the KEK Photon Factory. Our simulation successfully reproduces the modulation factor, defined as the ratio of the amplitude to the mean of the distribution of the azimuthal scattering angles, within similar to 5% (relative). Although primarily developed for the PoGOLite mission, the method presented here is also relevant for other missions aiming to measure polarization from astronomical objects using plastic scintillator scatterers.

  • 6.
    Kiss, Mózsi
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Larsson, S.
    Arimoto, M.
    Axelsson, A.
    Marini Bettolo, Cecilia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Bogaert, G.
    Floren, H. -G
    Fukazawa, Y.
    Gunji, S.
    Hjalmarsdotter, L.
    Kamae, T.
    Kanai, Y.
    Kataoka, J.
    Kawai, N.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kurita, K.
    Madejski, G.
    Mizuno, T.
    Olofsson, G.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ryde, Felix
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Rydström, Stefan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Ueno, M.
    Umeki, Y.
    Varner, G.
    Yoshida, H.
    The PoGOLite balloon-borne soft gamma-ray polarimeter2008In: COOL DISCS, HOT FLOWS: THE VARYING FACES OF ACCRETING COMPACT OBJECTS / [ed] Axelsson, M, 2008, Vol. 1054, p. 225-232Conference paper (Refereed)
    Abstract [en]

    Linearly polarized radiation in the hard X-ray/soft gamma-ray band is expected from a large variety of astronomical sources. We discuss the importance of polarimetric studies for several classes of sources - pulsars, accreting black holes. magnetic neutron stars and jets from active galaxies - and then describe PoGOLite, a balloon-borne instrument which is currently under construction and will be able to measure the polarization of electromagnetic radiation from such extra-solar objects in the energy range 25-80 keV.

  • 7.
    Marini Bettolo, Cecilia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Performance Studies and Star Tracking for PoGOLite2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    PoGOLite is a balloon-borne experiment, which will study polarized soft γ-ray emissionfrom astrophysical targets in the 25-80 keV energy range by applying well-typephoswich detector technology. Polarized γ-rays are expected from a wide variety of sources including rotation-powered pulsars, accreting black holes and neutron stars,and jet-dominated active galaxies. Polarization measurements provide a powerfulprobe of the γ-ray emission mechanism and the distribution of magnetic and radiation fields around the source. The polarization is determined using Compton scattering and photoelectric absorption in an array of 217 plastic scintillators. The sensitive detector is surrounded by a segmented Bismuth Germanium Oxide (BGO) anticoincidence shield. The function of this shield is to reduce backgrounds from charged cosmic rays, primary and atmospheric γ-rays, and atmospheric and instrumenta lneutrons. The anticoincidence shield consists of 427 BGO crystals with three different geometries. The characteristics of the BGO crystals of the bottom anticoincidence shield have been studied with particular focus on the light yield.The maiden flight of PoGOLite will be with a reduced detector volume “pathfinder” instrument. The flight, lasting about 24 hours, is foreseen from Esrange, Sweden in August 2010. The performance of the pathfinder has been studied using computer simulations. The effect of atmospheric attenuation, both on the signal of theastronomical target and on the background, are studied. These allow an observationstrategy to be developed for the forthcoming flight. A polarization analysis method is described and applied to an observation example. The method sets anupper limit on the accuracy with which the polarimeter will be able to detect polarization the angle and degree. The PoGOLite polarimeter has a relatively small field of view (2.4×2.4) which must be kept aligned to objects of interest on the sky. A star tracker forms part of the attitude control system. The star trackersystem comprises a CCD camera, a lens, and a baffle system. Preliminary studiesof the star identification performance are presented and are found to be compatible with the environment around the Crab, which is the main observational target for the first flight.

  • 8.
    Marini Bettolo, Cecilia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    PoGOLite: The Polarised Gamma-ray Observer2008Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    PoGOLite is a balloon-borne experiment which will study polarised soft gamma-ray emission from astrophysical targets in the 25 keV – 80 keV energy range by applying well-type phoswich detector technology. Polarised gamma-rays are expected from a wide variety of sources including rotation-powered pulsars, accreting black holes and neutron stars, and jet-dominated active galaxies. Polarisation measurements provide a powerful probe of the gamma-ray emission mechanism and the distribution of magnetic and radiation fields around the source. The polarisation is determined using Compton scattering and photoelectric absorption in an array of 217 plastic scintillators. The sensitive detector is surrounded by a segmented Bismuth Germanium Oxide (BGO) anticoincidence shield. The function of this shield is to reduce backgrounds from charged cosmic rays, primary and atmospheric gamma-rays, and atmospheric and instrumental neutrons. The anticoincidence shield consists of 427 BGO crystals with three different geometries. The characteristics of the BGO crystals of the bottom anticoincidence shield have been studied with particular focus on the light yield.

    The PoGOLite polarimeter has a field of view of 2.4° x 2.4° and must be kept aligned to objects of interest on the sky. A star tracker forms part of the attitude control system. The star tracker system comprises a CCD camera, lens, and a baffle system. Preliminary studies have been made concerning optimization of the focus, flat field correction, map of hot pixel and CCD response. An estimate of the star magnitude limit is also derived and found to be compatible with the environment around the Crab, which is the first observational target. These studies pave the way toward an autonomous star tracking device which together with the other attitude control devices will reconstruct the pointing solution.

  • 9.
    Marini Bettolo, Cecilia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    The PoGOLite Star Tracker System2009In: 2008 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (2008 NSS/MIC), 2009, p. 765-767Conference paper (Refereed)
    Abstract [en]

    PoGOLite is a balloon-borne experiment which will study polarised soft gamma-ray emission from astrophysical targets in the 25keV - 80keV energy range by applying well-type phoswich detector technology [1]. Polarised gamma-rays are expected from a wide variety of sources including rotation-powered pulsars, accreting black holes and neutron stars, and jet-dominated active galaxies. Polarization measurements provide a powerful probe of the gamma-ray emission mechanism and the distribution of magnetic and radiation fields around the source. The polarization is determined using Compton scattering and photoelectric absorption in an array of 217 plastic scintillators. The PoGOLite polarimeter has a field of view of 2.4 degrees x 2.4 degrees and must be kept aligned to objects of interest on the sky within 5% of the FOV to secure a minimum detectable polarization MDP=10% for a 200 mCrab source. This alignment can be obtained by mean of different attitude sensors: a DGPS (Differential Global Positioning System), two star trackers and gyroscopes. The most accurate sensor is the star tracker which is the focus of this paper. Preliminary studies [2] and calibration have been made which pave the way to an autonomous star tracking device which together with the other attitude control devices will reconstruct the pointing solution.

  • 10.
    Marini Bettolo, Cecilia
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kiss, Mózsi Bank
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics.
    Siegl, Martin
    KTH, School of Engineering Sciences (SCI), Physics.
    The BGO anticoincidence system of the PoGOLite balloon-borne soft gamma-ray polarimeter2007In: Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007 / [ed] Rogelio Caballero, Juan Carlos D’Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia, Universidad Nacional Autonoma de Mexico , 2007, Vol. 2, p. 483-486Conference paper (Refereed)
    Abstract [en]

    The PoGOLite balloon-borne experiment applies well-type phoswich detector technology tomeasurements of soft gamma-ray polarization in the 25 keV - 80 keV energy range. The polarization isdetermined using Compton scattering and photoelectric absorption in an array of 217 plastic scintillators.This sensitive volume is surrounded by a segmented bismuth germanate oxide (BGO) anticoincidenceshield, designed to reduce background from charged cosmic rays, primary and atmospheric gamma-rays,and atmospheric and instrumental neutrons. A total of 379 BGO crystals with three different geometriesare used, giving an overall mass of approximately 250 kg. Tests of the BGO crystals are described andthe overall design of the anticoincidence shield is reviewed.

  • 11. Mizuno, T.
    et al.
    Arimoto, M.
    Axelsson, Magnus
    Stockholm University.
    Björnsson, C. -I
    Bogaert, G.
    Carlson, Per
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Craig, W.
    Fukazawa, Y.
    Gunji, S.
    Hjalmarsdotter, L.
    Kamae, T.
    Kanai, Y.
    Kataoka, J.
    Katsuta, J.
    Kawai, N.
    Kiss, Mózsi Bank
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Larsson, S.
    Madejski, G.
    Bettolo, Cecilia M.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ng, J.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ryde, Felix
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Tajima, H.
    Takahash, H.
    Takahashi, T.
    Tanaka, T.
    Thurston, T.
    Ueno, M.
    Varner, G.
    Yoshida, H.
    High sensitivity balloon-borne hard X-ray/soft Gamma-Ray Polarimeter PoGOLite2007In: Nuclear Science Symposium Conference Record, 2007. NSS ’07. IEEE, IEEE , 2007, Vol. 4, p. 2538-2544Conference paper (Refereed)
    Abstract [en]

    The Polarized Gamma-ray Observer - Lightweight version (PoGOLite) is a new balloon experiment capable of detecting 10% polarization from a 200 mCrab source in the 25-80 keV energy range in a single 6-hour flight for the first time. Polarization measurements of hard X-rays and soft gamma-rays are expected to provide a powerful probe into high-energy emission mechanisms as well as source geometries. PoGOLite uses Compton scattering and photo-absorption to measure polarization in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators. The adoption of a well-type phoswich counter concept and a thick polyethylene neutron shield provides a narrow field-of-view (1.25 msr), a large effective area ( gt; 250 cm2 at 40-50 keV), a high modulation factor (more than 25%) and the low background ( 100 mCrab) required to conduct high-sensitivity polarization measurements. Through tests in laboratories and accelerator facilities of a scaled-down prototype with the front-end electronics of flight design and an extensive study by Monte Carlo simulation, we have demonstrated high instrument performance. PoGOLite will be ready for a first engineering flight in 2009 and a science flight in 2010, during which polarization signals from the Crab Nebula/pulsar, Cygnus X-1 and other objects will be observed.

  • 12. Takahashi, H.
    et al.
    Matsuoka, M.
    Umeki, Y.
    Yoshida, H.
    Tanaka, T.
    Mizuno, T.
    Fukazawa, Y.
    Kamae, T.
    Madejski, G.
    Tajima, H.
    Kiss, Mózsi Bank
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Larsson, Stefan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Bettolo, Cecilia Marini
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ryde, Felix
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Rydström, Stefan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kurita, K.
    Kanai, Y.
    Arimoto, M.
    Ueno, M.
    Kataoka, J.
    Kawai, N.
    Axelsson, Magnus
    Stockholm University.
    Hjalmarsdotter, L.
    Bogaert, G.
    Gunji, S.
    Katsuta, J.
    Takahashi, T.
    Varner, G.
    Yuasa, T.
    The Polarized Gamma-Ray Observer, PoGOLite2010In: Transactions of the Japanese Society for Artificial Intelligence, Aerospace Technology Japan, Vol. 8Article in journal (Refereed)
    Abstract [en]

    The Polarized Gamma-ray Observer, PoGOLite, is a balloon experiment with the capability of detecting 10% polarization from a 200 mCrab celestial object in the energy-range 25–80 keV. During a beam test at KEK-PF in 2008, 19 detector units and one anti-coincidence detector were assembled, and a 50 keV X-ray beam with a polarization degree of ∼90% was irradiated at the center unit. Signals from all 20 units were fed into flight-version electronics consisting of six circuit boards (four waveform digitizer boards, one digital I/O board and one router board) and one microprocessor (SpaceCube), which communicate using a SpaceWire interface. One digitizer board, which can associate up to 8 detectors, outputs a trigger signal. The digital I/O board handles the trigger and returns a data acquisition request if there is no veto signal (upper or pulse-shape discriminators) from any detector unit. This data acquisition system worked well, and the modulation factor was successfully measured to be ∼34%. These results confirmed the capabilities of the data-acquisition system for a “pathfinder” flight planned in 2010.

  • 13. Takahashi, H.
    et al.
    Matsuoka, M.
    Umeki, Y.
    Yoshida, H.
    Tanaka, T.
    Mizuno, T.
    Fukazawa, Y.
    Kamae, T.
    Madejski, G.
    Tajima, H.
    Kiss, Mózsi Bank
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Larsson, Stefan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Marini Bettolo, Cecilia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ryde, Felix
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Rydstrom, Stefan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kurita, K.
    Kanai, Y.
    Arimoto, M.
    Ueno, M.
    Kataoka, J.
    Kawai, N.
    Axelsson, M.
    Hjalmarsdotter, L.
    Bogaert, G.
    Gunji, S.
    Takahashi, T.
    Varner, G.
    Yuasa, T.
    Beam test results of the polarized gamma-ray observer, PoGOLite2008In: 2008 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (2008 NSS/MIC), VOLS 1-9, 2008, p. 732-736Conference paper (Refereed)
    Abstract [en]

    The Polarized Gamma-ray Observer, PoGOLite, is a balloon experiment with the capability of detecting 10% polarization from a 200 mCrab celestial object in the energy range 25 #x2013;80 keV. During a beam test at KEK-PF in February 2008, 20 detector units were assembled, and a 50 keV X-ray beam with a polarization degree of #x223C;90% was irradiated at the center unit. Signals from all 20 units were fed into flightversion electronics consisting of six circuit boards (four waveform digitizer boards, one digital I/O board and one router board) and one microprocessor (SpaceCube), which communicate using a SpaceWire interface. One digitizer board, which can associate up to 8 PDCs, outputs a trigger signal. The digital I/O board handles the trigger and returns a data acquisition request if there is no veto signal (upper or pulse-shape discriminators) from any detector unit. This data acquisition system worked well, and the modulation factor was successfully measured to be #x223C;34%. These results confirmed the capabilities of both detector and data-acquisition system for a pathfinder flight planned in 2010.

  • 14. Tanaka, T.
    et al.
    Arimoto, M.
    Axelsson, Magnus
    Stockholm University.
    Bjornsson, C. -I
    Bogaert, G.
    Carlson, Per
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Cooney, M.
    Craig, W.
    Engdegård, Olle
    KTH, School of Engineering Sciences (SCI), Physics.
    Fukazawa, Y.
    Gunji, S.
    Hjalmarsdotter, L.
    Kamae, T.
    Kanai, Y.
    Kataoka, J.
    Katsuta, J.
    Kawai, N.
    Kazejev, Jaroslav
    KTH, School of Engineering Sciences (SCI), Physics.
    Kiss, Mozsi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Larsson, Stefan
    Madejski, G.
    Bettolo, Cecilia Marini
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Mizuno, T.
    Ng, J.
    Nomachi, M.
    Odaka, H.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ruckman, L.
    Ryde, F.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Thurston, T.
    Ueno, M.
    Varner, G.
    Ylinen, T.
    Yoshida, H.
    Yuasa, T.
    Data acquisition system for the PoGOLite astronomical hard X-ray polarimeter2007In: 2007 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOLS 1-11, 2007, Vol. 1, p. 445-449Conference paper (Refereed)
    Abstract [en]

    The PoGOLite is a new balloon-borne instrument to measure the polarization of hard X-rays / soft gamma-rays in the 25-80 keV energy range for the first time. In order to detect the polarization, PoGOLite measures the azimuthal angle asymmetry of Compton scattering and the subsequent photo- absorption in an array of detectors. This array consists of 217 well-type phoswich detector cells (PDCs) surrounded by a side anti-coincidence shield (SAS) composed of 54 segments of BGO crystals. At balloon altitude, the intensity of backgrounds due to cosmic-ray charged particles, atmospheric gamma-rays and neutrons is extremely high, typically a few hundred Hz per unit. Hence the data acquisition (DAQ) system of PoGOLite is required to handle more than 270 signals simultaneously, and detect weak signals from astrophysical objects (lOOmCrab, 1.5 cs-1 in 25-80 keV ) under such a severe environment. We have developed a new DAQ system consisting of front-end electronics, waveform digitizer, field programmable gate array (FPGA) and a microprocessor. In this system, all output signals of PDC / SAS are fed into individual charge-sensitive amplifier and then digitized to 12 bit accuracy at 24MSa/s by pipelined analog to digital converters. A DAQ board for the PDC records waveforms which will be examined in an off-line analysis to distinguish signals from the background events and measure the energy spectrum and polarization of targets. A board for the SAS records hit pattern to be used for background rejection. It also continuously records a pulse-height analysis (PHA) histogram to monitor incident background flux. These basic functions of the DAQ system were verified in a series of beam tests.

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